This invention relates generally to a catheter having an expandable membrane or balloon at its distal tip. It is constructed so that it has two lumens; one is central lumen for a guidewire or for the introduction of drugs or vaso-occlusive materials or devices, and the other is coaxial about the interior lumen and is used solely for the purpose of inflating or deflating the distal inflatable membrane. The device is designed is such a way that it has a very narrow overall diameter and it is preferably constructed using a compliant balloon as the membrane. This is to say that the balloon section located distally on the inventive catheter is of the same general diameter as is the catheter shaft in the near neighborhood of the inflatable membrane, and yet will expand to as much as four or five times the diameter of the device when so inflated. Because of the very narrow configuration of the device, it may be used in regions of the body where prior balloon catheters are not suitable. This is to say that it may be used in the vasculature of the brain and the periphery as well as in the soft organs, such as the liver. It is of significantly small enough diameter that it may be used in various genito-urinary passageways without undue hardship on the patient. Also central to the invention is the use of a braid in the outside tubing assembly, desirably either metallic or of polymeric filaments. At least a portion of the inner tubing assembly of the inventive catheter, generally the more proximal portion, comprises a metallic braid, often a metallic or super-elastic alloy ribbon braid. This super-elastic alloy braid provides exceptional kink resistance, not just to the tubing assembly in which it is placed, but more surprisingly to the inner tubing assembly. The inner braid prevents the balloon from expanding during introduction of fluids through the inner lumen or the inner lumen from collapsing when the balloon is inflated. The inner tubing asembly also preferably comprises a coil section in the region of the inflatable membrane to provide enhanced flexibility.
Catheters having a coaxial structure are known. Many of them are used in procedures such as percutaneous transluminal angioplasty (PTA). In such procedures, however, the balloon is a noncompliant one. That is to say, it is of a specific size which is set upon the time of its manufacture. The balloon itself is folded or collapsed into a somewhat bulky and stiff region which is difficult to maneuver, both through the guiding catheter by which it is placed and through the various vascular lumen to the site of treatment. In such a procedure, a guiding catheter typically having a pre-shaped distal tip, is introduced into the vasculature of the patient. The catheter is then advanced from the entry site in the femoral artery up into the aorta. Once the tip of the catheter reaches the aorta, the distal end of the catheter is twisted or "torqued" so to turn the preshaped distal tip of that guiding catheter into the ostium of the desired coronary artery. A balloon-bearing catheter is then advanced through the guiding catheter and out its distal tip until the dilatation catheter's balloon extends across the region to be treated. The balloon is then expanded to the predetermined size, often by the use of a radio-opaque liquid at relatively high pressures. Upon completion of the procedure, the balloon is then deflated so that the dilatation catheter may be removed and thereafter the blood flow is restored through the thus-treated artery.
In other procedures, a balloon-bearing catheter, typically of a somewhat smaller diameter than a catheter used in PTA procedures might be used. In a universal sense, the procedure might be considered to be similar, since a guiding catheter is initially placed so that its distal end is near the site to be treated or diagnosed. The balloon catheter would then be placed through the lumen of the guiding catheter to that site. The balloon-bearing catheter, perhaps with a guidewire extending through an existing central lumen, could then be extended from the distal side of the guiding catheter to the treatment or diagnostic site. The balloon would then be expanded, and once the procedure is complete, the balloon deflated and removed from the body. In some instances, the balloon might be of a compliant nature rather than of a fixed diameter configuration found in a typical PTA balloon.
The advent of interventional radiology and its sub-practice, interventional neuroradiology, as a viable treatment alternatives in various regions of the body having tortuous vasculature often surrounded by soft organs, has produced demands on catheterization equipment not placed on devices used in PTA. The need for significantly smaller diameter devices and particularly those which have variable flexibility and are able to resist kinking is significant.
U.S. Pat. No. 5,338,295, to Cornelius, et al., describes a dilatation balloon catheter having a shaft formed of a tubular braid of a stainless steel material. The proximal outer tube section is encased in a polyimide material. The distal outer tube section which forms a balloon is made of a polymeric material such as polyethylene.
Another similar device is shown in U.S. Pat. No. 5,451,209, to Ainsworth, et al. Ainsworth, et al., describes a composite tubular element useful in intravascular catheters. In particular, it is said to be useful as an element of a fixed wire dilatation catheter or in a guiding or angiographic catheter. The structure of the device is formed by braiding strands which are formed from a mixture of a polymeric matrix material (e.g., a fiber or powder) having a relatively low melting point in a high strength reinforcing fiber having a relatively high melting point. The fibers are woven into a tubular element, the resulting braided tubular element is heated to melt the matrix material so to permit it to flow around the high melting point reinforcing fibers. This procedure forms a matrix. Thermoplastic jackets or coatings are then extruded onto or otherwise applied to the exterior of the thus-produced braided tubular element.
U.S. Pat. No. 5,429,597, to DeMello, teaches a balloon catheter which is said to be kink resistant. In general, it appears to be made up of an outer polymeric covering over a "cross-wound multifilar (CWMF) coil in a nonfixed removable core wire." The CWMF coil is a pair of helical coils which are wound in opposite directions so to provide torque transmission during use of the catheter. There appears to be no suggestion of weaving the CWMF materials into a braid.
PCT application to Pray, et al. (WO93-20881) assigned to SciMed Medical Systems suggests a dilatation catheter having a shaft with a proximal section which is a composite of polymeric materials and a stainless steel braid tube. The distal section of the catheter is formed of a flexible polymeric tube. In one embodiment of the described device, the braid weave of the proximal section of the shaft has a varying pick count, increasing in the distal direction. This provides for increased distal flexibility.
Published U.K. Patent Application GB-2,233,562A by Hannam, et al., shows a balloon catheter having a flexible, hollow inner shaft and an outer braided shaft with a balloon. The balloon is inflated by the use of fluid introduced between the inner and outer shafts. The inner shaft is fixed relative to the outer shaft at both ends, so that when the balloon is inflated, the outer shaft shortens. The excess length of the inner shaft is accommodated by the process of that inner shaft bending into a coil-like form within the outer shaft lumen. The braid is said typically to be of a fabric of a polyester floss. It is said to extend the entire length of the outer shaft but may include a varying pick rate apparently in the neighborhood of the balloon. The balloon is made of the same material as the braided layer, and has a flexible elastic polyurethane covering.
U.S. Pat. Nos. 5,032,113 and 5,476,477 to Burns, show a partially coaxial catheter having a region of the device which is coaxial in nature. The innermost lumen is used for passage of a guidewire. The outer annular lumen is used to inflate a balloon with which it is in hydraulic communication. The outer annular lumen is also in hydraulic communication with the inner lumen. A variety of flow reducing means are shown as being in mid-catheter to permit the passage of fluids at some controlled rate in and out of the balloon.
U.S. Pat. No. 5,460,607 shows another coaxial catheter in which the conventional balloon is open to an annular space between an inner and an outer tubing. One variation of the disclosed device is said (at column 12) to include a balloon made of a material such as polyurethane. In that variation, the inner tube (130) is said to be made of a hard tube, a metal spring reinforced tube, a fine stainless steel tube, etc.
U.S. Pat. No. 5,460,608 to Lodin, et al., shows a balloon catheter having an outer tubing shaft and an inner tubing shaft in which the inner shaft is constructed in such a way so as to "prevent it from collapsing or breaking" during use. It is said to be a dilatation catheter used in PTA in large peripheral vessels. The inner tubing is strengthened by the use of a reinforcing coil. The balloon is further said to be made preferably of polyethylene terephthalate.
U.S. Pat. No. 5,470,313, to Crocker et al, shows another variation of a balloon catheter with an inner and outer tubing assembly partially separated so to form a region between the two assemblies. The balloons described in conjunction with this device are not generally compliant, but are designed in such a way that they have variable diameters when inflated. This is done by the placement of bands at various sites around the circumference of the balloon.
U.S. Pat. No. 5,480,383, to Bagaoisan et al, is to a balloon catheter having an inner and outer tubular member with proximal portion of the inner tubular member being formed of a pseudoelastic alloy. The section appears to be tubular.
U.S. Pat. No. 5,480,380, to Martin, shows a dual lumen catheter in which the inner and outer lumens are equipped with orifices to allow materials placed within the catheters to perfuse into a selected treatment area.
None of the devices in the documents discussed above describe a catheter having the structure specified herein.